1. Field of the Invention
This invention relates to appliances and more particularly to a dishwasher having a special low washing liquid usage cycle.
2. Prior Art
Appliances, particularly dishwashers, are often provided with internal spraying devices for directing a stream of washing liquid at objects to be washed. In the case of dishwashers, it is known to provide washing chambers having a bottom sump with a motor driven pump positioned therein effective to supply washing liquid under pressure to a spraying device which directs a stream of washing liquid at dishes held in a rack positioned within the washing chamber. It has also been known to provide dishwashers having two dishracks disposed therein, one above the other, each being associated with a spraying device. The use of two spraying devices interiorly of the washing chamber provides improved washing of the dishes when separate dishracks are used.
It has been known to supply the two spraying devices with washing liquid from a common pump disposed in the sump. It has also been known to supply each of the spraying devices individually from two pumping devices disposed in the sump. Normally where two pumping devices are used, they are commonly driven by a separate motor and it has been known to axially space the pumping devices from one another with the lower pumping device providing washing liquid to the upper spray device and the upper pumping device providing washing liquid to the lower spray device. (See, for example, U.S. Pat. No. 3,179,307 to Duncan et al. and U.S. Pat. No. 3,084,701 to Hardy et al.) By disposing the pumping devices in a sump at the bottom of the washing chamber, it is assured that the pumping devices will be effectively supplied with washing liquid. In addition, this positioning allows the pumping devices to be used to drain the washing chamber, generally by reversal of the direction of rotation of the pumping devices, or, as disclosed in U.S. Pat. No. 2,629,390 to F. G. Walker, by utilizing a two-way valve.
Although such prior devices work effectively when there is a full load in the washing chamber, they are uneconomical when a partial load is being washed. In such instances, since both pumping devices are acting constantly to supply washing liquid to both spraying devices, a wasteful amount of washing liquid is utilized and an unnecessary amount of energy is expended in heating the washing liquid and in delivering the washing liquid to the spraying devices.
It would therefore be an advance in the art to provide a dishwasher having a special cycle delivering washing liquid to only one spray device during operation of the special cycle while being capable of delivering washing liquid to two spray devices during a normal cycle.
It is often desirable, in a dishwasher, to wash relatively fragile items such as, for example glassware, crystal, or the like by exposure to a more gentle spray than would be used to wash more rugged items such as pots and pans; and it has been known in the prior art to selectively provide such a gentle spray. See, for example, U.S. Pat. No. 2,990,835 to D. S. Cushing. It would be an advance in the prior art, however, to provide such a gentle wash action in a dishwasher having at least two dishracks disposed therein with a separate spray device associated with each wherein one of the spray devices provides a gentle spray and may be operated while the other spray device is inoperative when an energy-saving low fill condition is selectively provided.